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D. P. Biss, P. Zamiri, Y. Zhou, T. G. Bifano, R. H. Webb, C. P. Lin; A Sensorless Adaptive Optics Biomicroscope for Imaging Mouse Retina. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2854.
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© ARVO (1962-2015); The Authors (2016-present)
Adaptive optics imaging systems are powerful tools that allow cellular resolution of retina. Current adaptive optics systems employ wave front sensors to maximize the amount of light entering the confocal pinhole. The drawback of the system is that it measures wave fronts from multiple layers of the retina at the same time. In order to increase pinhole intensity and minimize the confusion that arises from light arriving from multiple sources in the wave front sensor, we have implemented a sensorless AO system.
We have integrated a sensorless adaptive optics system into an in vivo biomicroscope for fluorescence imaging of the mouse retina. The biomicroscope uses a long working distance 50x objective and provides imaging at video rate (30 fps) with an image field of approximately 0.5 mm square on the retina. A fluorescent excitation wavelength of 635 nm is used. The adaptive optics system utilizes the imaging PMT as feedback to control a Boston Micromachines MEMS deformable mirror with 3.5 micrometer stroke and 140 actuators. is used to optimize the mirror shape. A metric based on integrated image intensity is used for optimization.
Anesthetized C57BL/6 mice were placed on a heated microscope stage and their eyes were covered with a lubricating agent (Methocel). Evans Blue (0.2-1%) was injected intravenously to label the vasculature. All mice received a drop of tropicamide 1% to dilate the pupil. A glass cover slip was positioned on the anterior surface of the cornea for visualization. By using the confocal pinhole intensity as feedback, and a stochastic parallel gradient descent algorithm to control the deformable mirror, we have achieved aberration correction in mice without the use of a wavefront sensor. In a mouse injected with Evans blue image brightness and contrast was increased and capillaries were resolved.
Our results demonstrate that sensorless adaptive optics system is able to correct aberrations in murine retinal imaging. The sensorless adaptive optics system is simple, cheap and compact. It allows a greater light throughput and does not rely on wave front sensor.
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